This product was recommended by my ophthalmologist when I could no longer tolerate preservatives in eye drops. It's perfect for me as I use the drops many times a day, every day. I never discard any and take them with me everywhere I go. I only take unopened vials and use up any left in them when I get home. I find that if I twist the cap and break the seal, push the cap down as far as it will go, all the while twisting several times more, then I rarely have any trouble removing and replacing cap. This is a high quality product and I cannot imagine being without it. I only buy it from Well.ca. where I get ten boxes at a time at a better price than any store here in BC offers. Of course, the free shipping makes a difference. Fast shipping too.